1,4-Addition of arylboronic acids to β-aryl-α,β-unsaturated ketones and esters catalyzed by a rhodium(I)–chiraphos complex for catalytic and enantioselective synthesis of selective endothelin A receptor antagonists

Data Checking of Asymmetric Catalysis Literature Using a Graph Neural Network Approach

The range of chemical databases available has dramatically increased in recent years, but the reliability and quality of their data are often negatively affected by human-error fidelity. The size of chemical databases can make manual data curation/checking of such sets time consuming; thus, automated tools to help this process are highly desirable. Herein, we propose the use of Graph Neural Networks (GNNs) to identifying potential stereochemical misassignments in the primary asymmetric catalysis literature. Our method relies on the use of an ensemble of GNN models to predict the expected stereoselectivity of exemplars for a particular asymmetric reaction. When the majority of these models do not correlate to the reported outcome, the point is labeled as a possible stereochemical misassignment. Such identified cases are few in number and more easily investigated for their cause. We demonstrate the use of this approach to spot potential literature stereochemical misassignments in the ketone products resulting from catalytic asymmetric 1,4-addition of organoboron nucleophiles to Michael acceptors in two different databases, each one using a different family of chiral ligands (bisphosphine and diene ligands). Our results demonstrate that this methodology is useful for curation of medium-sized databases, speeding this process significantly compared to complete manual curation/checking. In the datasets investigated, human expert checking was reduced to 2.2% and 3.5% of the total data exemplars.

Highly Enantioselective Synthesis of 3,3-Diarylpropyl Amines and 4-Aryl Tetrahydroquinolines via Ir-Catalyzed Asymmetric Hydrogenation

Chiral nitrogen-containing compounds are crucial for the chemical, pharmaceutical, and agrochemical industries. Nevertheless, the synthesis of certain valuable scaffolds remains underdeveloped due to the vast chemical space available. In this work, we present a diastereoselective methodology for synthesizing 3,3-diarylallyl phthalimides, which, following iridium-catalyzed asymmetric hydrogenation using Ir-UbaPHOX, yield 3,3-diarylpropyl amines with high enantioselectivity (98-99% ee). The importance of alkene purity to achieve high enantioselectivity is discussed. The synthetic utility of the chiral propylamines obtained is demonstrated through the preparation of medicinally useful bioactive compounds like the drugs tolterodine and tolpropamine and 4-aryl tetrahydroquinolines. This strategy enables the synthesis of these compounds with the highest enantioselectivity reported to date.

Diastereoselective Construction of 2-Aminoindanones via an In(OTf)3-Catalyzed Domino Reaction

An In(OTf)₃-catalyzed domino reaction involving sequential oxidative ring opening of aziridines by using the solvent dimethyl sulfoxide and intramolecular Michael addition has been developed for the modular synthesis of 2-aminoindanone compounds by the formation of one new C═O bond and one new C-C bond. The notable feature of this strategy includes broad substrate scope, excellent trans-diastereoselectivities, highly functionalized products, and mild conditions. The catalyst In(OTf)₃ plays an important role in the formation of the indanone ring.

Theoretical investigations of Rh-catalyzed asymmetric 1,4-addition to enones using planar-chiral phosphine-olefin ligands

Recently, planar-chiral phosphine-olefin ligands based on (η⁶ -arene)chromium(0) and (η⁵ -cyclopentadienyl)manganese(I), which are known as first- and second-generation, respectively, have been developed. These ligands were employed for Rh-catalyzed asymmetric 1,4-addition to enones. First-generation ligands involve high enantioselectivity for cyclic enones (>98% ee). Second-generation ligands involve high enantioselectivity for not only cyclic enones but also for acyclic enones (>98% ee). In this study, we have performed DFT calculations to investigate the origin of enantioselectivity. The theoretical values of enantioselectivities were found to be in good agreement with the experimental values obtained for a cyclic enone, 2-cyclopenten-1-one, using both the first- and second-generation ligands. Regarding an acyclic enone, 3-penten-2-one, it was found that the s-cis type decreases the enantioselectivity because the transition states in the s-cis type have a large steric repulsion. Energy decomposition analysis (EDA) and natural bond orbital (NBO) analysis indicate that it is important to study the orbital interactions in the transition states of the insertion step for the acyclic enone attacked from si-face with the second-generation ligand. © 2018 Wiley Periodicals, Inc.

Stereoarrayed 2,3-Disubstituted 1-Indanols via Ruthenium(II)-Catalyzed Dynamic Kinetic Resolution-Asymmetric Transfer Hydrogenation

Activated racemic 2,3-disubstituted 1-indanones 1 possessing two stereolabile centers were stereoselectively reduced to the corresponding chiral 2,3-disubstituted-1-indanols 2 by ruthenium(II)-catalyzed dynamic kinetic resolution-asymmetric transfer hydrogenation. In particular, this route offers a practical access to a new class of conformationally rigid enantiopure 1,4-diols 2k-m having four contiguous chiral centers. Transformation of ent-2k into a Pallidol analogue via a highly diastereo- and regioselective Friedel-Crafts benzylation of o-chloroanisole is presented.

Enantioselective synthesis of gem-diarylalkanes by transition metal-catalyzed asymmetric arylations (TMCAAr)

To date, enantiomerically enriched molecules containing gem(1,1)-diaryl containing tertiary or quaternary stereogenic centers have been readily accessed by transition metal-catalyzed enantioselective or stereoconvergent aryl transfer reactions.

Chiral gem(1,1)-diaryl containing tertiary or quaternary stereogenic centers are present in many natural products and important pharmacophores. While numerous catalytic asymmetric methods enable access to 1,1-diaryl motifs, transition metal-catalyzed asymmetric arylations (TMCAAr) are one of the most powerful methods to prepare enantiopure gem-diarylalkane compounds. The main methodology includes enantioselective 1,2- or 1,4-additions across C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> O, C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> N and C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C bonds by arylmetallic reagents; aryl cross-couplings of olefins, benzylic (pseudo)halides and aziridines; asymmetric aryl substitution reactions of allylic substrates; and isotopic benzylic C–H arylation.

Nickel-Catalyzed Asymmetric Reductive Cross-Coupling To Access 1,1-Diarylalkanes

An asymmetric Ni-catalyzed reductive cross-coupling of (hetero)aryl iodides and benzylic chlorides has been developed to prepare enantioenriched 1,1-diarylalkanes. As part of these studies, a new chiral bioxazoline ligand, 4-heptyl-BiOX (L1), was developed in order to obtain products in synthetically useful yield and enantioselectivity. The reaction tolerates a variety of heterocyclic coupling partners, including pyridines, pyrimidines, indoles, and piperidines.

Synthesis of 1-indanones with a broad range of biological activity

This comprehensive review describes methods for the preparation of 1-indanones published in original and patent literature from 1926 to 2017. More than 100 synthetic methods utilizing carboxylic acids, esters, diesters, acid chlorides, ketones, alkynes, alcohols etc. as starting materials, have been performed. This review also covers the most important studies on the biological activity of 1-indanones and their derivatives which are potent antiviral, anti-inflammatory, analgesic, antimalarial, antibacterial and anticancer compounds. Moreover, they can be used in the treatment of neurodegenerative diseases and as effective insecticides, fungicides and herbicides.

Cooperativity of axial and centre chirality in the biaryl disulfoxide/Rh(i)-catalysed asymmetric 1,4-addition of arylboronic aids to 2-cyclohexenone: a DFT study

Atropisomeric biaryl disulfoxides contain two independent chiral elements. Previously, the (M,S,S)-diastereomer showed very high catalytic activity and selectivity in the Rh-catalyzed asymmetric 1,4-addition of arylboronic acids to α,β-enones whereas the (M,R,R) counterpart - none. Herein, DFT computations on the key transmetallation (turnover-determining) and carborhodation (enantioselectivity-determining) steps of the catalytic cycle show that the (M,S,S)-ligand gives rise to lower reaction barriers for these elementary steps. However, the barriers for the (M,R,R)-ligand are not sufficiently high to explain the lack of reactivity. Hence, this phenomenon is most likely due to the failure of catalyst formation from the ligand and the dimeric Rh precatalyst complex. The hitherto unknown (M,S,R)-ligand shows predicted enantioselectivity similar to the (M,S,S)-ligand as a consequence of lower reaction barriers associated with those isomers whose key features resemble the (M,S,S)-ligand.

Synthesis of chiral cyclobutanes via rhodium/diene-catalyzed asymmetric 1,4-addition: a dramatic ligand effect on the diastereoselectivity

A highly diastereo- and enantioselective rhodium-catalyzed arylation of cyclobutene-1-carboxylate esters for the efficient synthesis of chiral cyclobutanes has been developed.

Computational modelling of the enantioselectivity in the asymmetric 1,4-addition reaction catalyzed by a Rh complex of a S-chiral disulfoxide

Computational chemistry is a powerful tool for understanding chiral catalysis and can also aid future catalyst design.

Palladium(II)-catalyzed Heck reaction of aryl halides and arylboronic acids with olefins under mild conditions

A series of general and selective Pd(II)-catalyzed Heck reactions were investigated under mild reaction conditions. The first protocol has been developed employing an imidazole-based secondary phosphine oxide (SPO) ligated palladium complex (6) as a precatalyst. The catalytic coupling of aryl halides and olefins led to the formation of the corresponding coupled products in excellent yields. A variety of substrates, both electron-rich and electron-poor olefins, were converted smoothly to the targeted products in high yields. Compared with the existing approaches employing SPO-Pd complexes in a Heck reaction, the current strategy features mild reaction conditions and broad substrate scope. Furthermore, we described the coupling of arylboronic acids with olefins, which were catalyzed by Pd(OAc)2 and employed N-bromosuccinimide as an additive under ambient conditions. The resulted biaryls have been obtained in moderate to good yields.

1,4-Additions of arylboron, -silicon, and -bismuth compounds to α,β-unsaturated carbonyl compounds catalyzed by dicationic palladium(II) complexes

An enantioselective synthesis of cyclic and acyclic β-aryl ketone and aldehydes via Pd(II)-catalyzed 1,4-addition of Ar-m [m = B(OH)2, BF3K, Si(OMe)3, SiF3, BiAr2] to α,β-unsaturated ketones or aldehydes is described. The catalytic cycle involves transmetallation between Ar-m and Pd complexes as a key process, the mechanism of which is discussed on the basis of characterization of the transmetallation intermediate and electronic effect of the substituents. The enantioselection mechanism and efficiency of a chiraphos ligand for structurally planar α,β-unsaturated ketones are discussed on the basis of the X-ray structure of the catalyst and results of density functional theory (DFT) computational studies on the model of coordination of the substrates to the phenylpalladium(II)/(S,S)-chiraphos intermediate.